Development of a cheap wireless sensor node

Google for radio modem.

Anahata

What is "cheap"? It will be difficult to reach anything approaching "mass production cheap" if you are buying a preconstructed module. Note that there are plenty of off-the-shelf chip antennas; designing the antenna really isn't the hard part, building and tuning the rest of the circuit (and getting type approval) is the hard part.

What country are you in? The available frequencies/modules are different in different locales. Probably the simplest choice is something in the 2.4GHz ISM band.

A product like this is in your general ballpark and should give you an idea of the price to expect.

(500ft).

The replies were very helpful The problem is that the modules that i have seen are very costly (i

Short range for $5 is 10 feet.

Unless you don't care for FCC approved devices.

should

I am not concerned with the fcc approved devices This system is supposed to be a study project

This doesn't make sense. If it's a study project then the difference between $5 and $15 is negligible. If it's intended for production, then price matters and so does regulatory approval. What's it going to be?

I can say pretty confidently you will not be able to make or buy anything in prototype/hobbyist quantities that meets the specification. And the time and money you waste trying to engineer this solution will, at small volumes, dwarf the cost of just buying a known-good solution.